Porting TruthRivetTools to master

This code is used within the Higgs group for the truth-level classification of events. It needed some minor updates for Rivet and HepMC version migrations.

Note that this is used in derivation production ( @boeriu ).

Generators/GenInterfaces/GenInterfaces/IHiggsTruthCategoryTool.h

+/*
+  Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration
+*/
+
+/*
+ * Dual-use tool interface for Rivet routine for classifying MC events according to the Higgs template cross section categories
+ * Authors: Jim Lacey (Carleton University)
+ * <james.lacey@cern.ch,jlacey@physics.carleton.ca>
+ */
+
+#ifndef GENINTERFACES_IHIGGSTRUTHCATEGORYTOOL_H
+#define GENINTERFACES_IHIGGSTRUTHCATEGORYTOOL_H 1
+
+#include "AsgTools/IAsgTool.h"
+#include "HepMC/GenEvent.h"
+
+namespace HTXS {
+  class HiggsClassification;
+}
+
+class IHiggsTruthCategoryTool : public virtual asg::IAsgTool {
+ public:
+  ASG_TOOL_INTERFACE( IHiggsTruthCategoryTool ) //declares the interface to athena
+    virtual ~IHiggsTruthCategoryTool() {};
+ public:
+  virtual StatusCode initialize() = 0;
+  virtual StatusCode finalize () = 0;  
+  virtual HTXS::HiggsClassification* getHiggsTruthCategoryObject(const HepMC::GenEvent& HepMCEvent, const HTXS::HiggsProdMode prodMode)=0;
+};
+
+#endif //> !GENINTERFACES_IHIGGSTRUTHCATEGORYTOOL_H